1. Field of the Invention
The present invention relates to light shield blades for a light control device, and more particularly to an improvement on the light shield blades for use in a light control device for closing or reducing a light-passing aperture with plural blades such as a shutter or an automatic diaphragm, and to a light control device utilizing said light shield blades.
2. Description of the Prior Art
Mechanical light control devices, such as the shutter or automatic diaphragm employed in photographic cameras, include plural shield blades formed of a metal or a plastic material. High-speed movement of said blades improves the accuracy of short exposure times and allows synchronization of the electronic flash even in a short exposure time. Also reduced driving force required for the shutter or automatic diaphragm provides the advantages of easier film winding and longer service life of the shutter or diaphragm. The mass of the shield blades has to be decreased in order to achieve high-speed movement of the blades with reduced driving force, and, for this purpose it has been proposed, for example in the U.S. Pat. No. 4,298,265, to reduce the thickness of the blade on one or both faces thereof, while leaving the rim portion unchanged. Such thickness reduction, if applied on one face of the blade, will however cause bending of the blade because of the unbalanced residual stress, thus increasing the friction resistance between the blades or causing deterioration of the close contact between the overlapping blades, eventually giving rise to a defective light-shielding ability. On the other hand, in case of a blade with thickness reduction on both faces thereof, the rim portion thereof will no longer be in contact with the rim portion of another blade in the course of blade movement but will overlap with the thickness reduced area of the other blade, and the gap generated between said rim portion and said thickness reduced area will cause light leaking.